1. Field of the Invention
The present invention relates to a multistage gear-rolling apparatus. For instance, it is applicable to production of vehicle-flywheels having teeth and gears used in driving systems.
2. Description of the Related Art
Generally, gears have been produced by way of a hob-cutting step and a shaving finish-step with respect to a disk-shaped workpiece. In this technique, when an outer diameter and a facewidth of the gear are increased, producing efficiency is reduced and production costs are increased.
Accordingly, there has been developed a gear-rolling technique for generating gear-teeth by use of a rolling step. In accordance with this technique, since a rolling step in high temperatures is carried out, the teeth can be generated in an outer-circumferential portion of a workpiece. This rolling method is advantageous in decreasing costs in comparison with the method using the aforementioned hob-cutting step and shaving finish-step.
As for this gear-rolling method apparatus, a finishing rolling method apparatus has been disclosed in Japanese Unexamined Patent Publication (KOKAI) No.54-62,148. In this apparatus, as can be seen in FIG. 11, a set of rollers 203, having the first forming teeth 201 and the second forming teeth 202 disposed coaxially and longitudinally in series, are used. The first forming teeth 201 of the roller 203 are used for finish-rolling a first teeth portion 101 of a workpiece 100, and the second forming teeth 202 of the roller 203 are used for finish-rolling a second teeth portion 102 of the workpiece 100.
According to this conventional gear-rolling technique, after the workpiece 100 is set at a regular location, the first forming teeth 201 of the roller 203 are squeezed in the direction of the arrow "A1", and thereby the first teeth portion 101 are finish-rolled. Thereafter, the first forming teeth 201 are withdrawn in the direction of the arrow "A2".
Next, the workpiece 100 is relatively moved in the direction of the arrow "B1", that is, the axial direction. After that, the second forming teeth 202 of the roller 203 are squeezed in the direction of the arrow "A1", and thereby the second teeth portion 102 are finish-rolled.
Now, according to the gear-rolling technique disclosed in the above-mentioned publication, the rollers 203 are used not for rough-rolling but simply for finish-rolling. Therefore, this publication gear-rolling technique requires that the workpiece 100 formed by the rough-rolling apparatus is once removed from the rough-rolling apparatus and the workpiece 100 is reset to the finish-rolling apparatus having the roller 203 after the removal. Accordingly, there might arise fears in that an axial aberration of the workpiece 100 because of resetting the workpiece 100, roundness of the rolled gear is easy to be deteriorated; thus, the above-mentioned publication gear-rolling technique is disadvantageous in improving accuracy of the rolled gear because of resetting the workpiece 100.
Further, according to the above-mentioned publication technique, although the first forming teeth 201 and the second forming teeth 202 are disposed coaxially and in series in the axial direction, the first forming teeth 201 are used only for finish-rolling the first teeth 101 of the workpiece 100, similarly, the second forming teeth 202 are used only for finish-rolling the second teeth 102.
Moreover, according to the above-mentioned publication technique, when the first forming teeth 201 of the roller 203 begin engaging with the first teeth portion 101 of the workpiece 100 for the finish-rolling, this publication technique requires that an engaging special mechanism for engaging with the both smoothly. Similarly, when the second forming teeth 202 of the roller 203 begin engaging with the second teeth portion 102 of the workpiece 100 for the finish-rolling, this publication technique requires that an engaging special mechanism for engaging with the both smoothly.